Anti-Tip Chair Foot

ABSTRACT

Disclosed is an anti-tip chair leg extension device that is attachable to the foot of a chair leg to prevent or reduce the risk of the chair from tipping over backwards. This feature of the device is especially beneficial when a child is using the chair. The anti-tip leg extension device comprises: a leg socket mounted on a foot plate, grip keys and leg grips. The lower (or foot) portion of a rear leg of the chair leg is received into the leg socket. The leg grip wedge and key grip combination releaseably grips the foot of the chair leg when the chair leg is received in the leg socket. The foot plate then acts to shift the distance of the moment-arm of the chair backward and away from the center of mass of the chair to reduce a tendency of the chair to tip backward.

FIELD OF THE INVENTION

The present invention is in the field of devices for supporting the weight of a person in a seated position (Class 297). Specifically, the present invention relates to chairs having means to prevent the chair from falling over backwards (subclass 310). More specifically, the present invention is a leg attachment for aiding in the structural stability of the chair (subclass 463.1).

SUMMARY OF THE INVENTION

The present invention is an attachable anti-tip chair leg extension device. The leg extension device is “anti-tip” or “anti-tipping” in that it is attachable to the foot of a chair leg and improves the stability of the chair. That is, the anti-tip leg extension device prevents or reduces the risk of the chair from falling over backwards. This feature of the present invention is especially beneficial when a child is using the chair. As shown in FIGS. 1A & 1B and 2A & 2B, the anti-tip leg extension device comprises four primary components: a foot plate, a leg socket, grip keys and leg grips. The anti-tip leg extension device is intended to attach to the lower (or foot) portion of a chair leg on the two back legs of a chair.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an embodiment of the present attachable anti-tip chair leg extension device showing the opening of the leg socket.

FIG. 1B is a perspective view of the leg socket of the present attachable anti-tip chair leg extension device showing a relationship of the wedges of the gripping mechanism prior to being inserted into the opening of the leg socket.

FIG. 2A is a side elevation cross sectional view of the present attachable anti-tip chair leg extension device showing the relationship of the front and rear wedges of gripping means to the key ridges of the leg socket, and an alternative embodiment of a rear wedge grip.

FIG. 2B is a side elevation cross sectional view of the leg socket portion of the present attachable anti-tip chair leg extension device showing the relationship of the leg gripping means to a chair leg (in phantom) retained in the leg socket.

FIG. 3 is a front elevation cross sectional view of the present attachable anti-tip chair leg extension device showing a reinforcing bead or weld.

FIG. 4 is a rear elevation cross sectional view of the present attachable anti-tip chair leg extension device showing the leg receiver/socket mounted in a recess in the top-side of the foot plate.

FIGS. 5A & 5B are top plan views of the present attachable anti-tip chair leg extension device showing alternative embodiments of the opening of the leg socket, and an alternative foot plate configuration.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, the details of preferred embodiments of the present invention are graphically and schematically illustrated. Like elements in the drawings are represented by like numbers, and any similar elements are represented by like numbers with a different lower case letter suffix.

The present invention is an attachable anti-tip chair leg extension device 10. The leg extension device 10 is “anti-tip” or “anti-tipping” in that it is attachable to the foot of a chair leg 60 and improves the stability of the chair. That is, the anti-tip leg extension device 10 prevents or reduces the risk of the chair from falling over backwards. This feature of the present invention is especially beneficial when a child is using the chair. As shown in FIGS. 1A & 1B and 2A & 2B, the anti-tip leg extension device 10 comprises four primary components: a foot plate 12, a leg socket 14, grip keys 16 and leg grips 18. The anti-tip leg extension device 10 is intended to attach to the lower (or foot) portion 62 of a chair leg 60 (see FIG. 2B) on the two back legs of a chair.

The foot plate 12 has a front-portion 20 and a back-portion 22, a top-surface 24 and a bottom surface 26. The foot plate 12 is adapted to shift the distance of the moment-arm backward from the center of mass of the chair to reduce the tendency of the chair to rotate backward about an imaginary axis between the points of contact of the back legs of the chair and the floor on which the chair stands. The dimensions of the foot plate 12 in part depend on the configuration of the rear chair leg (i.e., the center of mass of the chair relative to the point of contact of the leg with the floor). It was found that a foot plate having an overall length L of about 4 to 8 inches and a width W of about 2 to 4 inches at its widest portion was generally satisfactory for a variety of rear leg configurations and chair types, with the rear chair leg 60 set back about an inch from the front-edge 30 of the plate 12. Thickness T of the foot plate 12 depends on the material composition of the plate itself. In a preferred embodiment the foot plate was composed of a rigid plastic material with a thickness T of ¼ inch. Depending on the style and weight of the particular chair the device 10 it to be used on, the foot plate 12 may need to be thicker. A wooden foot plate may need to be thicker, and a metal one might be thinner, as is selectable by one of ordinary skill in the art.

The leg socket 14 in a preferred embodiment was an oblong or square box, as generally shown in the figures. However, the leg socket 14 can have other configurations (see FIGS. 5A & 5B), so long as the interior portions of the front-side 42 and rear-side 44 of the leg socket includes wedge key 16 features to engage the leg grips 18. A particular configuration for the leg socket 14 is selectable by one of skill in the art depending in part on the configuration or variety of configuration chair leg 60 that the leg socket 14 is to receive. In the embodiments illustrated in FIGS. 3 & 4, the leg socket 14 was a 3 inch square box constructed of a ¼ inch thick rigid plastic material with about a 2.5 inch socket opening 40, and had an overall height H of about 4 inches.

The leg socket 14, into which a rear leg of a chair is receivable, has an upper-end 54 including an opening 40 into which a foot end 62 of the rear leg 60 of a chair is insertable, and a lower-end 56 mounted to the upper surface 24 of the foot plate 12. Additionally, the leg socket 14 has a front-side 42 and a rear-side 44. The front-side 42 is shorter than the other three sides of the leg socket 14, and is only about ⅔ of the overall height H of the leg socket 14. This created a gap in the front-side 42 which was continuous with the socket opening 40. The purpose of the gap is to facilitate inserting and seating the chair leg foot 62 in the leg socket 14. The front-side gap may be reduced or eliminated for a straight up & down chair leg or for a leg socket 14 having less overall height H.

A wedge key 16 is disposed on the interior surface of both the front-side 42 and the rear-side 44 of the leg socket 14 as shown in FIGS. 2A & 2B. The wedge key 16 is a ridge or lip that engages a key way 46 on a leg grip 18 (explained below). The rear-side wedge key 16 b is disposed proximate the upper-end opening 40 (see FIG. 3), and the front-side wedge key 16 a is disposed near the foot plate 12 at the lower-end of the leg socket 14 (see FIG. 4). The front-side wedge key 16 a positively retains and prevents from slipping the leg grip 18 that engages the lower portion of the foot 62 of the chair leg 60, while the back-side grip key 16 b positively retains and prevents from slipping the leg grip 18 that engages the foot 62 of the chair leg 60 at an upper portion of the foot 62 (see FIG. 2B).

The leg wedge grips 18 have a key-way 46 and a chair mating surface 48. The key-ways interface with the grip keys 16 of the leg socket 14 to help hold the wedge grips 18 in place when inserting a chair foot 62 into the leg socket, and to prevent the wedge grips 18 from sliding up or down once the chair foot 62 is in place in the device 10. The mating surface 48 is adaptable by the skilled artisan to increase the surface area of the wedge grips 18 that interface with the chair foot 62 as the skilled artisan considers useful. The combination of a grip key 16 with a leg grip 18 increases the stability of the present device 10 during use by reducing or eliminating the possibility of the leg grip slipping under a force and resulting in the chair leg 60 pulling out of the leg socket 14.

In a preferred embodiment of FIG. 2B, the leg grips 18 are substantially configured the same and can be used interchangeably. In an alternative embodiment, the rear grip 19 was configured as a wedge, which was inserted and jammed into the leg socket 14 behind the chair foot 62. In a preferred embodiment shown in FIG. 2A, the wedge grip 19 not only has a wedge shape, but also has detents 50 arranged as a series of saw teeth. When the wedge grip 19 is inserted into the leg socket 14 behind the chair foot 62, the detents progressively engage the grip key 16 of the rear-side of the leg socket 14. Once fully engaged, the detents limit the movement of the wedge grip 19 to prevent it from slipping out.

Typically, the lower-end of the leg socket 14 of the anti-tip chair leg extension device 10 is mounted to the top surface 24 of the foot plate 12, as illustrated in FIG. 3. To improve the strength of the mounting of the leg socket 14 to the foot plate 14, a reinforcing bead or weld 36 may be drawn along the interface of the leg socket 14 and the foot plate 12 as shown in FIG. 3. To further reinforce the anti-tip device 10 in the direction of the moment arm, a brace 58 can be added going from the rear-side 44 of the leg socket 14 to the top surface 24 of the foot plate 12. Additionally and/or alternatively, the foot plate 12 can be provided with a recess 34 in the front portion 20 of the top surface 24, with the recess 34 disposed for receiving and mounting the lower-end of the leg socket 14 to the foot plate 12 (see FIG. 4).

As shown in FIGS. 5A & 5B, the opening 40 of the leg socket 14 of the attachable anti-tip chair leg extension device 10 can be adapted to have a cross section which complements the shape of the chair foot 62 that it is intended to receive. Shown are square and circular openings 40 a & 40 b. Also illustrated is that the foot plate 12 can be configured in different shapes as are selectable by one of skill in the art.

While the above description contains many specifics, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of one or another preferred embodiment thereof Many other variations are possible, which would be obvious to one skilled in the art. Accordingly, the scope of the invention should be determined by the scope of the appended claims and their equivalents, and not just by the embodiments. 

What is claimed is:
 1. An anti-tip chair leg extension device (10) attachable to a foot (62) of a rear chair rear leg (60) comprising: a foot plate (12) having a front-portion (20) and a back-portion (22), a top-surface (24) and a bottom surface (26); a leg socket (14) into which the rear leg (60) is receivable, the leg socket (14) having an upper-end and a lower end, the upper-end having an opening (40) into which the foot end (62) of the rear leg (60) is insertable and the lower-end being mounted to the upper surface (24) of the foot plate (12), and having a front-side wedge grip key (16) for engaging the chair leg (60) at a lower portion of the foot (62) of the leg (60) and a back-side wedge grip key (16) for engaging the foot (62) of the chair leg (60) at an upper portion; and a leg grip wedge (18) adapted to engage the wedge key grip (16) and to releaseably grip the foot (62) of the chair leg (60) when the chair leg (60) is received in the leg socket (14), in combination to provide the device (10) adapted to shift the distance of a moment-arm of the chair backward from a center of mass of the chair to reduce a tendency of the chair to rotate backward.
 2. The attachable anti-tip chair leg extension device (10) of claim 1, wherein the lower-end of the leg socket (14) is mounted to the top surface (24) of the foot plate (12).
 3. The attachable anti-tip chair leg extension device (10) of claim 1, wherein the the foot plate (12) has a recess (34) in the front portion (20) of the top surface (24), the recess (34) for receiving and mounting the lower-end of the leg socket (14) to the foot plate (12).
 4. The attachable anti-tip chair leg extension device (10) of claim 1, wherein the opening of the leg socket has a cross section adapted to closely receive a shape of the foot (62) of the chair leg (60).
 5. The attachable anti-tip chair leg extension device (10) of claim 1, wherein the leg socket (14) is further mounted to the top surface (24) of the foot plate (12) by a brace (58) from the rear-side (44) of the leg socket (14) to the top surface (24) of the foot plate (12).
 6. The attachable anti-tip chair leg extension device (10) of claim 1, wherein the leg grip (19) has a wedge shape with detents (50) arranged as a series of saw-tooth like projections. 